Cis-pent-2-enyl-1-chloride is a valuable substance useful in the preparation of cis-jasmone which, in turn, is a valuable substance useful in the formulation of perfume materials. The cis-jasmone can be prepared according to the reaction: ##STR2## wherein X is chloro and wherein M is alkali metal. Such a reaction is more specifically exemplified in U.S. Pat. No. 4,045,489 issued on Aug. 30, 1977 wherein the reaction is carried out (1) using a "phase transfer agent" and (2) in a two phase system.
The reaction of a Grignard reagent with an alkenyl dihalide is well known in the prior art. Thus, a paper by Mesnard and Miginiac appearing at Compte Rendus Acad. Sc. Paris, T277 (Oct. 8, 1973) at pages 567-570 discloses, generically, the reaction sequence: ##STR3## wherein X is halogen and wherein R is lower alkyl. Specifically exemplified is the reaction between methyl magnesium iodide and trans 1,4-dibromo-2-butene.
The specific reaction of our invention as described by the reaction scheme: ##STR4## is not taught by Mesnard and Miginiac.
Thus, the Mesnard and Miginiac reference does not fulfill the need for producing a pure or substantially pure cis-pent-2-enyl-1-chloride, in one step without the need for an expensive physical separation step whereby the cis-pent-2-enyl-1-chloride is separated from the reaction mass. According to the teaching of Mesnard and Miginiac if cis-pent-2-enyl-1-chloride were produced it would be a minor product and 4-chloro-3-methyl-1-butene would be the major product.
Cis-2-penten-ol is produced from 1-chloro-4-hydroxy-2-butene by reaction with methyl magnesium bromide according to the teachings of Kagiwara et al, Agr. Biol. Chem., 39 (1), 243-247, 1975. The problems associated with reaction of a dihalide rather than the hydroxyl halide compound of Kagiwara et al are quite evident. Accordingly, the Kagiwara et al teaching is not predictive of the production of substantially pure cis-pent-2-enyl-1-chloride by the process of the instant invention.
Kharasch, U.S. Pat. No. 2,404,235 discloses a reaction of a vinyl halide and an aryl Grignard or aryl-alkyl Grignard reagent according to the reaction: ##STR5## in which X is halogen, R is an aryl radical such as phenyl or anphthyl or an aryl-aliphatic radical such as benzyl and Y, R.sub.1 and R.sub.2 and R.sub.3 are as follows:
Y is a halogen; PA1 R.sub.1 is hydrogen, lower alkyl, or aromatic; PA1 R.sub.2 and R.sub.3 are selected from the group consisting of hydrogen and lower alkyl but are both hydrogen when R.sub.1 is aromatic.
The Kharasch reaction is a reaction different in kind from the reaction of our process. The disclosure of the reaction of a vinyl halide and a Grignard reagent in general does not give rise to predictability of the reaction of an allyl halide and Grignard reaction as is the case in our process.